We have previously suggested that the gal operon of E. coli has two promoters; ne promoter is subject to positive control by cyclic AMP and cyclic AMP receptor protein and the other promoter to negative control by the cyclic AMP nucleotide and its receptor protein. The structure of these promoters is being analyzed. We have shown that the operon also carries signals for transcription termination by the termination factor rho not only at the end of the operon but also within it. We have proposed that polarity of gene expression of an operon is because of premature transcription termination within an operon. This is supported by the isolation and characterization of various types of E. coli mutants defective in transcription termination factor rho. The control of gene expression in temperate bacteriophages lambda and P22 is also based on overcoming transcription termination at specific signals. A similar regulatory gene has been identified in lambda and P22 that prevents transcription termination. We are analyzing the mechanisms of action of these regulatory genes. We are also studying the effect of lambda development on host cell physiology.